Inflatable mattresses are used in hospital rooms, old age homes, and other applications in which a person is required to spend long periods of time restricted to a bed. A common problem for patients requiring such long-term care is the development of decubitus ulcers, or bed sores, caused by excessive pressure applied to a patient's contact points. A patient's weight on a bed can cause a counter force to be applied to the patient's body from the bed at points where the patient's body contacts the bed. Although contact points can be present across the body, it is common for sick and disabled individuals who are bed bound to develop tissue damage on the heels of the feet, on the ankle, and/or on other parts of the body. This tissue damage to the heels is generally the result of an individual lying in a supine position where the heels bear the weight of the legs on the surface of the mattress. Alternatively, if the individual is in a sidelying position, the ankle will bear the weight of the legs against the mattress. Often, this pressure exceeds the ability of the capillaries to circulate blood to the cells which results in an isohemic condition. Lacking blood supply, these cells die causing the tissue damage.
In known continuous flow, low air loss mattresses, air is used to expand the mattress to a desired pressure. Air is allowed to escape the air mattress through small holes located on the top of the mattress. These holes serve to maintain a constant mattress pressure against the patient and provide air flow between the patient and the mattress to remove humidity created by the patient's body. This feature keeps the mattress dry, accelerates the healing process, and helps prevent bed sores. An example of one such air loss system is disclosed in U.S. Pat. No. 4,896,389 to Chamberland.
Leg elevation is a commonly employed method of removing pressure from heels in the supine position and from the ankles in a sidelying position. This is frequently accomplished by placing pillow or wedges under and/or between the legs of the individual on the mattress.
A mattress that includes multiple inflatable air chambers to assist in relieving pressure from contact points for bed bound patients is disclosed in U.S. Pat. No. 4,953,247 to Hasty. These inflatable mattresses have varied the pressure in specific chambers to help contour the mattress and apply equal force throughout the patient's body.
U.S. Pat. No. 5,666,681 to Meyer et al. discloses a device for relieving pressure on a patient's heels and/or ankles by employing multiple air chambers under the patient's heels that are located within the mattress. A first air chamber directly under the heels deflates allowing the heels to sink down into the mattress while the pressure of a second forwardly adjacent air chamber increases to lift the calves to further reduce the stress on the heels.